spdep (version 0.2-9)

read.gal: Read a GAL lattice file into a neighbours list

Description

The function reads a GAL lattice file into a neighbours list for spatial analysis. It will read old and new style (GeoDa) GAL files. read.geoda is a helper file calling read.csv().

Usage

read.gal(file, region.id=NULL, override.id=FALSE)
read.geoda(file, row.names=NULL, skip=0)

Arguments

file

name of file with GAL lattice data

region.id

region IDs in specified order to coerse neighbours list order and numbering to that of the region.id

override.id

override any given (or NULL) region.id, collecting region.id numbering and order from the GAL file.

row.names

as in row.names in read.csv(), typically a character string naming the column of the file to be used

skip

skip number of lines, as in read.csv()

Value

• The function returns an object of class nb with a list of integer vectors containing neighbour region number ids.

warning

The column names read by read.geoda() change between R releases 1.8.x and 1.9.0, because the underscore character becomes a valid character from that release.

Details

Luc Anselin (2003): Spatial Analysis Laboratory, Department of Agricultural and Consumer Economics, University of Illinois, Urbana-Champaign, http://sal.agecon.uiuc.edu/weights/howto.html; Luc Anselin (2003) GeoDa 0.9 User's Guide, pp. 80--81, Spatial Analysis Laboratory, Department of Agricultural and Consumer Economics, University of Illinois, Urbana-Champaign, http://agec221.agecon.uiuc.edu/csiss/pdf/geoda093.pdf; GAL - Geographical Algorithms Library, University of Newcastle

See Also

summary.nb

Examples

us48.fipsno <- read.geoda(system.file("etc/weights/us48.txt",
 package="spdep")[1])
us48.q <- read.gal(system.file("etc/weights/us48_q.GAL", package="spdep")[1],
 us48.fipsno$Fipsno)
us48.r <- read.gal(system.file("etc/weights/us48_rk.GAL", package="spdep")[1],
 us48.fipsno$Fipsno)
data(state)
if (as.numeric(paste(version$major, version$minor, sep="")) < 19) {
 m50.48 <- match(us48.fipsno$"State.name", state.name)
} else {
 m50.48 <- match(us48.fipsno$"State_name", state.name)
}
plot(us48.q, as.matrix(as.data.frame(state.center))[m50.48,])
plot(diffnb(us48.r, us48.q),
 as.matrix(as.data.frame(state.center))[m50.48,], add=TRUE, col="red")
title(main="Differences between rook and queen criteria imported neighbours lists")